I got this aswer from Asus, when I requested a Core 2 supporting bios for my reworked P5WD2-E board:

"After checked with our RD, due to the normal life circle of our product, P5WD2-E Premium doesn’t support Conroe before PCB 1.03G rev.

So even you change the VRM, due to the circuit limitation, the 1.02G rev motherboard still will not work with Conroe CPU."